spapr_pci: populate ibm,loc-code

spapr_pci: populate ibm,loc-code

Each hardware instance has a platform unique location code.  The OF
device tree that describes a part of a hardware entity must include
the “ibm,loc-code” property with a value that represents the location
code for that hardware entity.

Populate ibm,loc-code.

1) PCI passthru devices need to identify with its own ibm,loc-code
   available on the host. In failure cases use:
   vfio_<name>:<phb-index>:<bus>:<slot>.<fn>

2) Emulated devices encode as following:
   qemu_<name>:<phb-index>:<bus>:<slot>.<fn>

Signed-off-by: Nikunj A Dadhania <[email protected]>
Signed-off-by: David Gibson <[email protected]>
Signed-off-by: Alexander Graf <[email protected]>